Simple molecular structures have what kind of melting and boiling points?

• A. Low
• B. High
• C. Very high
• D. Moderate

Answer: (A)

Simple molecular structures only hold molecules together with weak intermolecular forces, not with strong bonds in a solid lattice. When a substance melts or boils, you mainly have to overcome these forces between molecules, which takes relatively little energy. That’s why they tend to have low melting and boiling points—you don’t need much energy to separate the molecules. Some simple molecules with larger dispersion forces can have slightly higher points, but they remain much lower than those of ionic or giant covalent substances. So, the best description is low melting and boiling points.